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Space Flight/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim and Moby are walking in front of NASA Headquarters. Tim holds an apple. He points off-screen. TIM: Yeah, I think that's the way. Tim and Moby stand at the entrance to an exhibit called: Rocket Garden. MOBY: Beep. TIM: No, they don't grow rockets. Men and women build them by hand, piece by piece with meticulous attention to detail and a refined sense of . . . MOBY: Beep. Tim realizes that he and Moby are blocking others from entering the exhibit. TIM: Oh, sorry. Tim steps aside. A man hands him a typed letter. Tim reads it. TIM: Dear Tim and Moby, how do spacecraft go into outer space? From, Dana. That's a great question, Dana. Now, here's one for you. Have you ever noticed that when you throw something into the air, it always comes back down? Tim holds up the apple he has been carrying. TIM: That's because the force of gravity pulls small objects, like this apple, toward larger objects, like the planet Earth. You might have also noticed that tossing an object just a few feet into the air isn't so difficult. Tim tosses and catches the apple. TIM: But if you want to get something way up there, you've really got to put your back into it. Tim grunts as he tosses the apple much higher this time. One of Moby's arms extends and catches it as it falls back down. MOBY: Beep. TIM: Yep, that's the key problem that scientists needed to solve when they first dreamed of leaping off the planet. How can you produce enough energy to throw an object so far up that it doesn't come back? MOBY: Beep. TIM: Well, where outer space begins depends on your definition of space. But most people consider the cutoff to be about a hundred kilometers above sea level. You need a lot of force to propel an object that far, and that's where rockets come in. A rocket is basically a device that burns fuel to create an expanding gas. An image shows a rocket. TIM: This gas shoots out the bottom of the rocket, pushing it with massive force. An animation shows the rocket ignite and take off. TIM: That force is known as thrust, and it propels the rocket upward. It's the same principle as jumping. Your legs push on the ground and your body goes up. An animation illustrates Tim's explanation, using a rising rocket and an upward arrow labeled, Thrust. TIM: In order for an object to lift off the ground, the thrusting force must be greater than the force of gravity. A downward arrow labeled, Gravity appears below the upward arrow labeled, Thrust. TIM: The more massive an object is, the more gravity acts upon it, so you can imagine the kind of thrust it takes to lift a giant rocket 100 kilometers into the air. MOBY: Beep. TIM: Well, there are two main types of fuel, or propellant, that a rocket can burn: liquid and solid. A liquid-fuel rocket is a good choice when you have a heavy load to launch into space, since liquids can be stored in lightweight tanks. An image shows a diagram of a liquid-fuel rocket. Its fuel and oxidizer tanks are labeled. TIM: In this type of rocket, liquid fuel is mixed with another chemical called an oxidizer. When the oxidizer meets with the fuel in the presence of a spark or flame, an explosion occurs. The explosion creates rapidly expanding gas, which generates thrust. An animation shows a liquid-fuel rocket launching. TIM: Then you have solid-fuel rockets. These burn a mixture of oxidizer and fuel that's solid at room temperature. An image shows a diagram of a solid-fuel rocket. Its igniter, propellant, and nozzle cone are labeled. TIM: When it's ignited, the exhaust gases get expelled through the rocket's end nozzle. MOBY: Beep. TIM: Oh, it can be any number of chemicals, depending on the rocket. Some use black powder fuel, which is kind of like what's inside fireworks. Others use sugars like dextrose or sucrose. Anyway, when they launch, rockets start off with a lot of fuel, which is heavy. But as the fuel burns, the rocket gets lighter, so it can go faster and faster until it reaches the speed required to get into space. MOBY: Beep. TIM: Well, all spacecraft need rocket power to leave the planet. An animation shows a spacecraft taking off. TIM: Often, the payload, or main part of a spacecraft, is attached to the top of the rocket, and then disconnected from the lower part once it reaches a certain altitude. An animation shows a rocket in space releasing a satellite. TIM: Many spacecraft are launched this way; telecommunications satellites, planetary probes, you name it. And quite a few piloted spacecraft, like the Apollo capsules of the nineteen-sixties and seventies, and the Soyuz capsules of today, have the same basic setup. Other times, reusable launch systems are used. The U.S. space shuttle was a partially reusable system. An image shows a space shuttle set for launch. TIM: It launched with an orbiter which glided back to Earth, two solid-fuel booster rockets that would fall into the ocean and get reused, and an external tank containing liquid fuel. Graphics point out the parts of the shuttle as Tim names them. TIM: The external tank thrust the orbiter all the way into space, but then disconnected and fell back to Earth, breaking up before it landed. MOBY: Beep. TIM: Right. Many objects that launch into space stay close enough to Earth to remain under the planet's gravitational pull. An image shows a satellite orbiting Earth. TIM: But some spacecraft go way farther than that. Those with their own propulsion systems can travel to the far reaches of the solar system. An image shows a probe drifting over one of Saturn's moons. Tim notices that Moby is gone. TIM: Uh, Moby? Moby's voice is heard in the distance. MOBY: Beep. Tim turns his head. Moby is standing with a group of young people. TIM: Oh, you're not really going to-- Moby takes off like a rocket. TIM: Showoff! Category:BrainPOP Transcripts Category:BrainPOP Engineering & Technology Transcripts Category:BrainPOP Science Transcripts